Seed piece spacing influences yield, tuber size distribution, stem and tuber density, and net returns of three processing potato cultivars

Seed piece spacing is an important economic consideration in the production of potatoes (Solanum tuberosum L.), The optimum spacing varies with cultiv ar and intended market. A study was designed to determine the influence of seed piece spacing on yield, tuber size distribution, net returns, and stem and tuber density of three processing potato cultivars. Seed tubers of cul tivars Russet Burbank, Frontier Russet, and Ranger Russet were planted 8, 1 5, 23, 31, 46, 61, 76, or 91 cm apart at two locations in 1988 and 1989. To tal, marketable (U.S. No. 1), and midsize (226-452 g tubers) yield, tuber s ize distribution, net profits from a representative processing contract, an d stem and tuber density (number per meters of row) were determined. All th ree cultivars achieved highest total yields at the narrowest (8 cm) spacing . Maximum marketable and midsize (226-452 g) yield occurred between 15 and 31 cm, depending on the cultivar, Size distribution shifted from a predomin ance of small tubers at narrow spacings to a predominance of large tubers a t wide spacings, and the rate of shift was cultivar-dependent. 'Russet Burb ank' showed a broad range of optimal spacing for net returns, with a maximu m in the range of 23 to 46 cm. Optima for 'Frontier Russet' and 'Ranger Rus set' were between 15 and 46 cm. Of the four tuber measurements, midsize yie ld appeared to be best for determining optimum spacing. Marketable yield wa s also a useful measurement. All three cultivars gave maximum midsize yield s at a stem density of 10.5 to 12.1 per meter of row and a tuber density of 23.9 to 24.9 per meter of row. Tuber density showed some promise as a pred ictor of optimum seed piece spacing for new cultivars.